Contribution of Femtosecond Laser Filaments to Positive and Negative Breakdown Discharge in Long Air Gap

The guidance probability of a positive discharge reached at most 15% during the dark period stage, leading to little effect on the breakdown discharge probability, whereas, for negative discharges, the guidance probability could exceed 95%. Discussion of the filament contribution to both polarity discharges found that the different migration directions of photoelectrons led to a difference in the effects of laser filaments on inception voltages, and the difference in the connection of the two discharge passages led to a difference in the guidance probability.

Through a simulation model, it was speculated that the connection condition for positive discharges was that the positive leader superimposed the laser filaments, and, for negative discharges, the rod electrode was connected to the laser filaments through a bi-directional discharge propagation.